The present invention relates to apparatus for supporting double entry centrifugal gas compressors and for maintaining the axial component of the compressor rotor running clearances.
Double entry centrifugal compressors are known per se and representative applications of these devices can be found in e.g. U.S. Pat. No. 2,438,426 (Whittle).
A problem caused by the twin, axially opposed compressor entrances occurs in applications where the compressor drive apparatus and the components for receiving the compressed gas are positioned axially adjacent the double entry compressor, such as in a gas turbine engine. This problem involves the thermal expansion of the cross-over ducts caused by compressed air heating during compressor operation which, if not accommodated in some manner, can cause shifts in the axial position of the compressor housing relative to that of the compressor rotor, a situation leading to unwanted changes in compressor rotor running clearance or increased component stress levels.
The prior art solution for this problem was to utilize a relatively rigid connection between the compressor housing and the axial adjacent engine components in conjunction with flexible bellows connections for the cross-over ducts to absorb the thermal expansion/contraction. While acceptable for the relatively low pressure ratios (i.e. less than about 6:1) characteristic of prior art double entry radial compressors, the bellows connection may be inadequate for the new generation of double entry radial compressors such as is disclosed in U.S. Pat. No. 577,359 where pressure ratios greater than about 6:1 are expected.